Abstract— A series of retinals with specific structural alterations have been synthesized to probe the bacteriorhodopsin binding site. The 4‐chloro‐, 4‐bromo‐ and 4‐iodoretinals all form pigments with bacterioopsin but undergo an in situ displacement of the allylic halogen to form the 4‐hydroxyretinal pigment. Several naphthyl retinals were prepared which effectively extend the polyene chain and/or add bulk to the ring portion of the chromophore. All the naphthyl retinals form pigments with bacterioopsin but only the pigment containing the derivative with a polyene side chain identical to that of retinal pumps protons efficiently. The 12‐butyl‐13‐desmethylretinal was also synthesized but this analogue did not form a pigment with bacterioopsin. These results confirm the nonspecificity at the ring portion of the chromophore binding site and the importance of the role of the polyene chain in the proton pumping function of bacteriorhodopsin.

Die 2‐cis‐ und all‐trans‐Isomere der acyclischen Retinale (I) bilden mit Bacterioopsin Pigmente, die gegenüber Hydroxylamin empfindlich sind, bei 4°C Lichtadaption zeigen und als dunkeladaptienes Pigment den 2‐cis‐ und all‐trans‐ bzw. den all‐trans‐Chromophor enthalten.

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Die 2‐cis‐ und all‐trans‐Isomere der acyclischen Retinale (I) bilden mit Bacterioopsin Pigmente, die gegenüber Hydroxylamin empfindlich sind, bei 4°C Lichtadaption zeigen und als dunkeladaptienes Pigment den 2‐cis‐ und all‐trans‐ bzw. den all‐trans‐Chromophor enthalten.